The present invention relates to heat shields and it is concerned particularly, but not exclusively, with heat shields for use in metal processing.
For instance, in the processing of a hot steel strip in a rolling mill, a hot product is taken through several working stages to produce a finished strip. The metallurgical qualities and gauge of the finished strip are closely related to the accurate control of the temperature of the material during the hot rolling process. However, due to heat losses occurring through radiation and convection it is extremely difficult to control the temperature through its various working stages which may require some time delay between stages thereby resulting in the product not having its required rolling and finishing temperatures.
Attempts in various forms, such as aluminum reflectors or heat insulating panels located along the delay table of a finishing mill have been used to reduce the heat losses from the surfaces of a hot product. These attempts have serious limitations which as to the reflectors are discussed in the background portion of Laws, U.S. Pat. No. 4,463,585, which is referred to herein for providing additional background information for a better understanding of the present invention.
As mentioned in this '585 patent, one type of heat insulating panel has a heat insulating core and a flat cover plate forming a main face of the panel; and as disclosed in this same patent, another type of heat insulating panel provides for relative thermal expansion of a thin, flat plate with respect to the core. In both types, the entire outer surface of the plate is directly exposed to the heated object and the plate is backed up by insulation. Also, both types are adapted so that the thin flat plates are temperature resistant material which absorb and then radiate heat back to the heated object or product. It is mandatory that the plate's dimension be such as to provide sufficient effective heat emissivity of its surface without melting and its temperature be able to quickly rise to closely approach the temperature of the product to re-radiate the heat and reach thermal equilibrium with the product.
It is therefore an object of the present invention to provide a re-radiating heat shield having a surface area with a substantially high heat emissivity and thermal capacity substantially equivalent to the panels of the present designs however commencing to re-radiate heat and approach thermal equilibrium with the heated product in a much quicker period of time with a less temperature drop in the heated product compared to the panels of the present designs.
It is a further object of the present invention to provide a heat shield for re-radiating heat comprising thermal insulating material having a number of closely adjacent co-extending sections provided with one or more holding surfaces formed by said adjacent sections, thermal absorbing material having a portion directly exposable to a heat source which portion includes a series of relatively short co-extending surfaces, said thermal absorbing material also including for each said short surface a substantially co-extending longer surface arranged not to be directly exposed to said heat source, said longer surfaces of said thermal absorbing material arranged to enwrap at least a portion of a different one of said co-extending sections of said thermal insulating material and restrained by said holding surfaces of two adjacent sections of said insulating material, wherein the nature and thermal mass of said thermal absorbing material and the nature and relationship of said thermal insulating material relative thereto greatly increases the re-radiating thermal characteristics of said thermal absorbing material.
More particularly, the present invention provides a design for a re-radiating panel having a sheet of refractory fiber material arranged in a sinuous manner to form a block, and a relatively thin sheet of heat storing material such as stainless steel arranged adjacent to the sides of the fiber sheet such that it conforms to the fiber sheet's sinuous configuration with portions of the stainless steel sheet doubling over into folds and which folds fit tightly in the folds of the fiber block for support and strengthed thereby and where heat is stored and other relatively shorter portions of the stainless steel sheet being exposed to the atmosphere.